Amorphous alloy for magnetic core material

ABSTRACT

There is disclosed an amorphous alloy for a magnetic core material represented by the formula 
     
         (Co.sub.1-x.sbsb.1.sub.-x.sbsb.2 Fe.sub.x.sbsb.1 
    
      M x .sbsb.2) x .sbsb.3 B x .sbsb.4 Si 100-x .sbsb.3 -x .sbsb.4 
     wherein M is at least one element selected from the group consisting of Ti, V, Cr, Mn, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W and Re, and x 1 , x 2 , x 3  and x 4  are numbers which satisfy relations of 0≦x 1  ≦0.10, 0≦x 2  ≦0.10, 70≦x 3  ≦79 and 5≦x 4  ≦9, respectively. 
     According to the present invention, it could be provided an amorphous alloy suitable for a magnetic core material of a magnetic amplifier in which its coercive force is as low as 0.4 oersted or less at a high frequency of 20 KHz or more, particularly even at 50 KHz, and its rectangular ratio is as much as 85% or more.

BACKGROUND OF THE INVENTION

The present invention relates to an amorphous alloy, more particularly to an amorphous alloy usuable as a magnetic core material for a magnetic amplifier or the like and having a low coercive force in a high frequency and excellent rectangular characteristics.

As a stabilized power source for the peripheral unit of a computer and a general communication device, in recent years, a switching power source carrying a magnetic amplifier has widely been used.

A main portion constituting a magnetic amplifier is a saturable reactor, and a magnetic core material excellent in rectangular magnetizing characteristics is now required for a core of the saturable reactor.

Heretofore, as such a magnetic core material, there has been used Sendelta (trade mark) comprising a Fe--Ni crystalline alloy.

However, being excellent in rectangular magnetinzing characteristics, Sendelta increases in coercive force in a high frequency of 20 KHz or more, whereby its eddy-current loss becomes great, so that it evolves heat and finally cannot be used any more. For this reason, in the case of a switching power source, the frequency has been limited to 20 KHz or less.

On the other hand, it is lately required to further heighten the switching frequency, along with demands for miniaturization and weight-saved of a switching power source, but a satisfactory magnetic core material having less coercive force at a high frequency and simultaneously having excellent reactangular characteristics has not been found yet until now.

SUMMARY OF THE INVENTION

The inventors of the present application have researched with much enthusiasm with the intention of overcoming such problems as mentioned above, and have finally found that when a cobalt series amorphous alloy is prepared under the requirements that boron and silicon are included in predetermined atomic parcentages and a crystallization temperature (Tx) is higher than a Curie temperature (Tc), the thus obtained amorphous alloy has a low coercive force in a high frequency of 20 KHz or more and is excellent in rectangular magnetizing characteristics. And, this finding has led to the completion of the present invention.

An object of the present invention is to provide an amorphous alloy suitable for a magnetic core material of a magnetic amplifier in which its coercive force (Hc) is as low as 0.4 oersted (Oe) or less at a high frequency of 20 KHz or more, particularly even at 50 KHz, and its rectangular ratio (Br/B₁) is as much as 85% or more.

This is to say, according to the present invention, there is provided an amorphous alloy for a magnetic core material represented by the formula

    (Co.sub.1-x.sbsb.1.sub.-x.sbsb.2 Fe.sub.x .sbsb.1 M.sub.x.sbsb.2).sub.x.sbsb.3 B.sub.x.sbsb.4 Si.sub.100-x.sbsb.3.sub.-x.sbsb.4

wherein M is at least one element selected from the group consisting of Ti, V, Cr, Mn, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W and Re, and x₁, x₂, x₃ and x₄ are numbers which satisfy relations of 0≦x₁ ≦0.10, 0≦x₂ ≦0.10, 70≦x₃ ≦79 and 5≦x₄ ≦9, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of an apparatus for preparing an amorphous alloy by using single roll method;

FIG. 2 shows relation curves between ratios x of the component B and rectangular ratios Br/B₁ as well as coercive forces Hc in regard to amorphous alloys of the composition (Co₀.92 Fe₀.06 Nb₀.02)₇₇ B_(x) Si_(23-x) according to the present invention;

FIG. 3 shows relation curves between test frequencies f and coercive forces Hc of thin bodies, which are distinct in thickness, in regard to the amorphous alloy of the composition (Co₀.88 Fe₀.06 Nb₀.02 Ni₀.04)₇₆ B₉ Si₁₅ according to the present invention; and

FIG. 4 shows a switching power source circuit including a magnetic amplifier in which there is used a saturable reactor comprising the amorphous alloy of the composition (Co₀.90 Fe₀.06 Cr₀.04)₇₇ B₈ Si₁₅ according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, the present invention is described more detail.

In the composition of the amorphous alloy according to the present invention, the component Fe contributes to the increase in the magnetic flux density of an alloy which will be obtained, and its component ratio X₁ is such that the relation of 0≦x₁ ≦0.10 is satisfied. It is undesirable that the ratio x₁ exceeds 0.10, because a magnetic strain of an alloy increases as a whole and thereby a coercive force (Hc) goes up.

The element M (one or more of Ti, V, Cr, Mn, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W, and Re) is concerned in the thermal stability of an alloy, and its composition ratio x₂ is such that relation of 0≦x₂ ≦0.10 is satisfied. When the ratio x₂ exceeds 0.10, it will be hard to obtain an amorphous product. Of these elements represented by the element M, those which are highly effective and thus useful are Nb, Ta, Mo and Cr. The three above-mentioned components (Co, Fe and M) are determined so that the ratio x₃ of the total amount thereof may be in the relation of 70≦x₃ ≦79. In the case that the ratio x₃ is less than 70, it will be difficult to prepare a product in the amorphous form. On the other hand, when it exceeds 79, a crystallization temperature (tx) of an alloy will fall below a Curie temperature (Tc), and thereby as a whole it will be impossible to provide the alloy with a low-coercive force.

In the amorphous alloy according to the present invention, semi-metallic elements of B and Si are essential for the preparation of an amorphous product, and when the ratio x₄ of the component B is less than 5, it will be difficult to obtain an amorphous alloy. However, when it exceeds 9, a rectangular ratio of magnetic characteristics will be reduced. Accordingly, the ratio x₄ of the component B is to lie in the relation of 5≦x₄ ≦9.

The composition of the amorphous alloy of the present invention is preferred that the above-mentioned x₁, x₂, x₃ and x₄ are numbers which satisfy relations of 0.04≦x₁ ≦0.07, 0.01≦x₂ ≦0.04, 73≦x₃ ≦77 and 6.5≦x₄ ≦9, respectively.

It is well known that an amorphous alloy can generally be prepared by quenching an alloy material including the respective components in predetermined ratios, from its molten state at a cooling rate of 10⁵ ° C./sec. or more (a liquid quenching method) (see, for example, IEEE Trans. Mag. MAG-12 (1976) No. 6, 921), thereby thin body is obtained having thickness of 10 to 50 μm. This quenching method can be carried out, for example, as shown in FIG. 1. In FIG. 1, starting alloy A is placed in a heating vessel 1 made of aluminum or quartz and fused under heating by using a high frequency heating furnace 2. The resultant molten alloy is ejected from a nozzle 3 which is mounted at the bottom of the heating vessel under gaseous pressure onto the surface of a roll 4 rotating at high speed (peripheral speed of 15 to 50 m/sec.), and then is drawn out as a thin body 5.

The amorphous alloy according to the present invention may be used in the form of a tape-like thin body which is prepared by an above-mentioned ordinary single roll method. In this case, it is usually preferred that a thin body has a thickness of 10 to 25 μm, since it is substantially difficult to prepare a thin body of 10 μm or less in a thickness by means of the quenching method.

In the following, the present invention will be explained on the basis of given Examples:

EXAMPLES 1-5

Thin bodies were prepared from amorphous alloys having a variety of compositions shown in Table 1 by use of an ordinary single roll method. Each thin body was about 5 mm in width and was 18 to 22 μm in thickness.

These strips of one meter in length were cut off from the thin bodies and were wound around bobbins of 20 mm in diameter in order to prepare toroidal cores. Afterward, each of the thus obtained cores was subjected to a heat treatment at a suitable temperature between a crystallization temperature (Tx) or less and a Curie temperature (Tc) or more, and then each sample was wholly dipped into water (25° C.) for quench.

Around each of the obtained cores a primary and a secondary winding were provided, and alternating hysteresis values were measured under an outer magnetic field of 1 Oe by use of an alternating magnetization measuring equipment. From curves of the obtained hysteresis values, coercive forces Hc and rectangular ratios Br/B₁ (Br and B₁ represent a residual magnetic flux density and a magnetic flux density in a magnetic field of 1 Oe, respectively) were evaluated. Table 1 exhibits the Hc and the Br/B₁ values of the thin bodies at each high frequency of 20 KHz, 50 KHz and 100 KHz. For comparison, corresponding values of conventional Sendelta is together shown therein.

                                      TABLE 1                                      __________________________________________________________________________                       Coercive force Rectangular ratio                                               Hc (0e)        Br/B.sub.1 (%)                                       Composition                                                                               20 KHz                                                                              50 KHz                                                                              100 KHz                                                                             20 KHz                                                                              50 KHz                                                                              100 KHz                             __________________________________________________________________________     Example 1                                                                             (Co.sub.0.94 Fe.sub.0.06).sub.77 B.sub.8 Si.sub.15                                        0.185                                                                               0.250                                                                               0.275                                                                               90.0 91.5 95.5                                Example 2                                                                             (Co.sub.0.96 Fe.sub.0.04).sub.77 B.sub.8 Si.sub.15                                        0.195                                                                               0.270                                                                               0.310                                                                               87.2 89.5 92.1                                Example 3                                                                             (Co.sub.0.92 Fe.sub.0.08).sub.75 B.sub.9 Si.sub.16                                        0.210                                                                               0.290                                                                               0.330                                                                               86.5 88.5 90.5                                Example 4                                                                             (Co.sub.0.97 Nb.sub.0.03).sub.77 B.sub.8 Si.sub.15                                        0.200                                                                               0.270                                                                               0.350                                                                               90.8 92.5 96.5                                Example 5                                                                             Co.sub.78 B.sub.7 Si.sub.15                                                               0.210                                                                               0.280                                                                               0.315                                                                               87.1 88.7 90.6                                Comparative                                                                           Sendelta   0.92 >1   >1   98.0 99.0 99.0                                Example 1                                                                      __________________________________________________________________________

As understood from Table 1, the amorphous alloys according to the present invention had Hc values of 0.4 Oe or less and Br/b₁ values of 85% or more. On the contrary, in regard to conventional Sendelta used, the Br/B₁ value was great but the Hc value was also disadvantageously great, and, above all, under the conditions of a high frequency of 50 KHz or more and an outer magnetic field of 1 Oe, measurement of Hc value was impossible.

This fact indicates that Sendelta is unsuitable as a magnetic core material at a high frequency.

EXAMPLES 6-10

Thin bodies were prepared from amorphous alloys represented by the formula (Co₀.92 Fe₀.06 Nb₀.02)₇₇ B_(x) Si_(23-x) in the same manner as in Examples 1-5 except that the amount of the component B was variously changed (i.e., the ratio x of the component B was altered), and for each of the resultant bodies, Hc and Br/B₁ values were measured. The results obtained are exhibited in FIG. 2, in which symbols o and • represent the Hc and Br/B₁ values, respectively.

As is definite from FIG. 2, the sample having the ratios x of 5, 6, 7, 8 and 9 (Examples 6, 7, 8, 9 and 10) showed rectangular ratios Br/B₁ of 85% or more, at a frequency of 50 KHz but in the samples having the ratios x of 10 and 11 (Comparative examples 2 and 3), rectangular ratios were below 85%. The results suggest that the ratio x of the component B must be such that it satisfies the relation of 5≦x≦9.

In this connection, samples having the ratios x of less than 5 took no amorphous state.

EXAMPLES 11-28

Thin bodies were prepared from amorphous alloys having compositions shown in Table 2 in which the component M is changed, by use of a single roll method. Each of the resultant thin bodies has a thickness of 18 to 22 μm.

Toriodal cores were prepared from these thin bodies in the same manner as in Examples 1-5, and around each of the prepared cores a primary and a secondary winding were provided. Then, alternating hysteresis values of the cores were measured under an outer magnetic field of 1 Oe by use of an alternating magnetization measuring equipment. From curves of the obtained hysteresis values, coercive forces Hc and rectangular ratios Br/B₁ were evaluated at a frequency of 50 KHz.

Further, these cores were subjected to an aging treatment in a constant temperature bath of 120° C. for 1000 hours, and then Hc and Br/B₁ values were measured again. The results obtained are shown in Table 2. For comparison, value of a sample not including any component M is together exhibited therein.

                                      TABLE 2                                      __________________________________________________________________________                         Before aging                                                                              After aging                                            Composition  Hc (0e)                                                                             Br/B.sub.1 (%)                                                                       Hc (0e)                                                                             Br/B.sub.1 (%)                             __________________________________________________________________________     Example 11                                                                            (Co.sub.0.91 Fe.sub.0.06 Ti.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.23 93.0  0.25 92.5                                       Example 12                                                                            (Co.sub.0.91 Fe.sub.0.06 V.sub.0.03).sub.77 B.sub.8 Si.sub.15                               0.23 93.0  0.25 92.0                                       Example 13                                                                            (Co.sub.0.91 Fe.sub.0.06 Cr.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.21 94.0  0.21 93.5                                       Example 14                                                                            (Co.sub.0.91 Fe.sub.0.06 Mn.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.23 92.0  0.24 92.0                                       Example 15                                                                            (Co.sub.0.91 Fe.sub.0.06 Ni.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.23 92.5  0.24 92.0                                       Example 16                                                                            (Co.sub.0.91 Fe.sub.0.06 Zr.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.23 91.5  0.25 91.0                                       Example 17                                                                            (Co.sub.0.91 Fe.sub.0.06 Nb.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.19 95.5  0.19 95.0                                       Example 18                                                                            (Co.sub.0.91 Fe.sub.0.06 Mo.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.20 94.0  0.20 94.0                                       Example 19                                                                            (Co.sub.0.91 Fe.sub.0.06 Ru.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.23 92.0  0.24 92.0                                       Example 20                                                                            (Co.sub.0.91 Fe.sub.0.06 Hf.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.24 92.0  0.25 91.5                                       Example 21                                                                            (Co.sub.0.91 Fe.sub.0.06 Ta.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.20 93.5  0.20 93.5                                       Example 22                                                                            (Co.sub.0.91 Fe.sub.0.06 W.sub.0.03).sub.77 B.sub.8 Si.sub.15                               0.20 92.0  0.20 91.0                                       Example 23                                                                            (Co.sub.0.91 Fe.sub.0.06 Re.sub.0.03).sub.77 B.sub.8 Si.sub.15                              0.24 91.0  0.26 90.0                                       Example 24                                                                            (Co.sub.0.97 Ti.sub.0.03).sub.77 B.sub.8 Si.sub.15                                          0.28 96.0  0.29 96.0                                       Example 25                                                                            (Co.sub.0.97 Cr.sub.0.03).sub.77 B.sub.8 Si.sub.15                                          0.26 94.0  0.27 94.0                                       Example 26                                                                            (Co.sub.0.97 Nb.sub.0.03).sub.77 B.sub.8 Si.sub.15                                          0.24 96.5  0.24 96.5                                       Example 27                                                                            (Co.sub.0.97 Ru.sub.0.03).sub.77 B.sub.8 Si.sub.15                                          0.25 96.0  0.25 95.5                                       Example 28                                                                            (Co.sub.0.96 Mo.sub.0.02 Ta.sub.0.02).sub.77 B.sub.8 Si.sub.15                              0.26 96.0  0.27 96.0                                       Comparative                                                                           (Co.sub.0.94 Fe.sub.0.06).sub.77 B.sub.20 Si.sub.3                                          0.28 90.5  0.35 84.3                                       Example 4                                                                      __________________________________________________________________________

The results in Table 2 above indicate that the amorphous alloys according to the present invention (Examples 11 to 28) have low coercive forces, high rectangular characteristics and excellent thermal stabilities. Particularly, these effects are pronounced in the cases that the component M is Nb, Mo, Ta or Cr.

EXAMPLES 29-32

Thin bodies of 12 μm, 18 μm, 22 μm and 25 μm in thickness were prepared from amorphous alloys according to the present invention having the composition formula

    (Co.sub.0.86 Fe.sub.0.06 Nb.sub.0.02 Ni.sub.0.04).sub.76 B.sub.9 Si.sub.15

in a single roll method by changing a roll revolution number. For these bodies, coercive forces Hc were measured at a variety of high frequencies in the same way as in Examples 1-5, and obtained results are shown in FIG. 3. For comparison, thin body of 27 μm in thickness was prepared, and its result was also shown therein.

As FIG. 3 elucidates, samples of 12 μm, 18 μm, 22 μm and 25 μm in thickness (Examples 29, 30, 31 and 32) had as low Hc values as 0.4 Oe or less even at 50 KHz. On the other hand, as to a sample of 27 μm in thickness (Comparative example 5), the measured Hc value exceed 0.4 Oe at 50 KHz or more, which fact indicates that such a body is too thick and impractical for use as a magnetic core material.

EXAMPLE 33

A thin body of 16 μm in thickness was prepared from an amorphous alloy having the composition

    (Co.sub.0.90 Fe.sub.0.06 Cr.sub.0.04).sub.77 B.sub.8 Si.sub.15

and then a toroidal core was manufactured in the same manner as in Examples 1-5. The core was thermally treated at a temperature of 430° C. (Tc=500° C. and Tx=380° C.) and was then quenched in water.

The resultant core was utilized for a magnetic amplifier of the circuit shown in FIG. 4 in order to examine its performance as a switching power source for 100 KHz-operation. Measurement was made for efficiency (output/input×100(%)), temperature rise of the core (°C.) and exciting current (mA). Referring now to FIG. 4, reference numeral 6 is an input filter, 7 is a switch, 8 is a transformer, 9 is a magnetic amplifier, 10 is a rectifier, 11 is an output filter and 12 is a control zone. The results obtained in the above manner are exhibited in Table 3. For comparison, results according to the employment of Sendelta are also described therein.

                                      TABLE 3                                      __________________________________________________________________________                               Temperature                                                                    rise of                                                                               Exciting                                                          Efficiency                                                                           cores  current                                       Composition         (%)   (°C.)                                                                          (mA)                                          __________________________________________________________________________     Example                                                                              (Co.sub.0.90 Fe.sub.0.06 Cr.sub.0.04).sub.77 B.sub.8 Si.sub.15                               80.2  38     80                                            33                                                                             Comparative                                                                          Sendelta      70.0  85     740                                           Example                                                                        __________________________________________________________________________

As understood from Table 3, in the amorphous alloy according to the present invention, the efficiency improved about 10% more than Sendelta, the exciting current was as low as 1/9 of Sendelta, and the temperature rise of the core was also small. Therefore, it has been found that the amorphous alloy according to the present case is a highly excellent magnetic material.

In consequence, the amorphous alloy according to the present invention has as small a coercive force as 0.4 Oe or less in a high frequency and has as large a rectangular ratio of 85% or more, which fact means that the amorphous alloy according to the present invention is useful for a magnetic core of a magnetic amplifier or the like and is concluded to be greatly valuable in industrial fields. 

We claim:
 1. An amorphous alloy for a magnetic core material consisting essentially of the formula

    (Co.sub.1-x.sbsb.1.sub.-x.sbsb.2 Fe.sub.x.sbsb.1 M.sub.x.sbsb.2).sub.x.sbsb.3 B.sub.x.sbsb.4 Si.sub.100-x.sbsb.3.sub.-x.sub.di 4

wherein M is at least one element selected from the group consisting of Ti, V, Cr, Mn, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W and Re, and x₁, x₂, x₃ and x₄ are numbers which satisfy relations of 0≦x₁ ≦0.10, 0≦x₂ ≦0.10, 70≦x₃ ≦79 and 5≦x₄ ≦9, respectively, said amorphous alloy after aging having a rectangular ratio Br/B₁ of at least 85% at 50 KHz, wherein Br represents residual magnetic flux density and B₁ represents a magnetic flux density in magnetic field of 1 oersted.
 2. An amorphous alloy according to claim 1, wherein x₁, x₂, x₃ and x₄ are numbers which satisfy relations of 0.4≦x₁ ≦0.07, 0.01≦x₂ ≦0.04, 73≦x₃ ≦77 and 6.5≦x₄ ≦9, respectively.
 3. An amorphous alloy according to claim 1, wherein M is at least one selected from the group consisting of Nb, Ta, Mo and Cr.
 4. An amorphous alloy according to claim 1, wherein said alloy is a thin body of 25 μm or less in thickness.
 5. An amorphous alloy according to claim 4, wherein said alloy is a thin body of 10 to 25 μm in thickness.
 6. An amorphous alloy for a magnetic core material consisting essentially of the formula

    (Co.sub.1-x.sbsb.1.sub.-x.sbsb.2 Fe.sub.x.sbsb.1 M.sub.x.sbsb.2).sub.x.sbsb.3 B.sub.x.sbsb.4 Si.sub.100-x.sbsb.3.sub.-x.sbsb.4

wherein M is at least one element selected from the group consisting of Ti, V, Mn, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W and Re, and x₁, x₂, x₃ and x₄ are numbers which satisfy relations of 0≦x₁ ≦0.10, 0≦x₂ ≦0.10, 70≦x₃ ≦79 and 5≦x₄ ≦9, respectively.
 7. An amorphous alloy according to claim 6, wherein x₁, x₂, x₃ and x₄ are numbers which satisfy relations of 0.04≦x₁ ≦0.07, 0.01≦x₂ ≦0.04, 73≦x₃ ≦77 and 6.5≦x₄ ≦9, respectively.
 8. An amorphous alloy according to claim 6, wherein M is at least one element selected from the group consisting of Nb, Ta and Mo.
 9. An amorphous alloy according to claim 6, wherein said alloy is a thin body of 25 m or less in thickness.
 10. An amorphous alloy according to claim 9, wherein said alloy is a thin body of 10 to 25 m in thickness.
 11. A toroidal core material comprising an amorphous alloy consisting essentially of the formula

    (Co.sub.1-x.sbsb.1.sub.31 x.sbsb.2 Fe.sub.x.sbsb.1 M.sub.x.sbsb.1).sub.x.sbsb.3 B.sub.x.sbsb.4 Si.sub.100-x.sbsb.3.sub.x.sbsb.4

wherein M is at least one element selected from the group consisting of Ti, V, Cr, Mn, Ni, Zr, Nb, Mo, Ru, Hf, Ta, W and Re, and x₁, x₂, x₃ and x₄ are numbers which satisfy relations of 0≦x₁ ≦0.10, 0≦x₂ ≦0.10, 70≦x₃ ≦79 and 5≦x₄ ≦9, respectively.
 12. A toroidal core material according to claim 11, wherein x₁, x₂, x₃ and x₄ are numbers which satisfy relations of 0.04≦x₁ ≦0.07, 0.01≦x₂ ≦0.04, 73≦x₃ ≦77 and 6.5≦x₄ ≦9, respectively.
 13. A toroidal core material according to claim 11, wherein M is at least one element selected from the group consisting of Nb, Ta, Mo and Cr.
 14. A toroidal core material according to claim 11, wherein said alloy is a thin body of 25 m or less in thickness.
 15. A toroidal core material according to claim 14, wherein said alloy is a thin body of 10 to 25 m in thickness. 